SE Area of Interest--10% two day, 40% five day odds

[WxWatcher007]

Ok, so normally we wouldn't have threads for current low probability systems, but I guess we're changing that this year. This comes from my bigger overview, which highlights this area of interest. I've been quietly watching for days, and now it's worth discussion. 

This area of potential has been much more interesting than 95L, and has been for a while now for the reasons below. Yesterday most probably sat up as the happy hour GFS showed a strong system attempt to develop in the wake of 95L off the same frontal boundary, this time getting shunted back into the US. Well, although that run of the GFS was way too aggressive, the signal for some sort of follow up development has been on the guidance for a few days now. It's not terribly hard to see why, as the environment looks at least marginally favorable for some development. 

Vorticity

First--the frontal boundary is usually good for getting some vorticity spin up. This fits with climatology. So if something is far enough off the coast there should be some sort of spin that develops in the coming days. Both models pick up on this in the medium range. 

This is not enough for TC genesis. Which leads to the second favorable factor.

Instability

While the tropical Atlantic has been incredibly stable so far this season...

There has been no such issue off the East Coast...in fact, instability has been extremely high. 

What that tells me is that anything that does have spin and can develop an area of low pressure will have a chance to generate convection, which will only help with TC genesis odds as long as the system isn't hugging land the entire time. 

SSTa

Not much analysis needed here. I expect the the southwest Atlantic to be a hotbed of activity this season because that's where the heat is. Any low is going to have a shot with enough time and space to become tropical in this SSTa regime. 

Shear

The key inhibitor here is shear. Often times with these frontal boundary systems near the coast you have shear and drier air that is lurking. That comes with the territory with the frontal boundary. Here it is unclear how favorable a shear environment this potential system will find, but guidance is hinting at a window of lower shear later this week taking hold. 

What makes this particularly interesting is the steering pattern. While the outcome is different in terms of where the area of vorticity goes, the pattern evolution is the same. In the wake of 95L a ridge builds in and traps whatever could develop along the coast. That's something to legitimately watch. Maybe not closely, yet, but at least with a casual eye.  

[BarryStantonGBP]

7 minutes ago, WxWatcher007 said:

In before Barry takes the thread lol. Working on a real OP. 

Hi!

 

3. Off the Southeastern United States:
An area of low pressure could form in a couple of days a few hundred 
miles southeast of the Carolinas.  Some gradual development of this 
system is possible by midweek as the system drifts to the 
northwest. 
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.

[WxWatcher007]

7 minutes ago, BarryStantonGBP said:

Hi!

 

3. Off the Southeastern United States:
An area of low pressure could form in a couple of days a few hundred 
miles southeast of the Carolinas.  Some gradual development of this 
system is possible by midweek as the system drifts to the 
northwest. 
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.

I had to beat you to the punch haha

[BarryStantonGBP]

Just now, WxWatcher007 said:

I had to beat you to the punch haha

it is ogre 

chances this develops into a bonafide tc?

[GaWx]

Upped from 20% to 30%:

2. Off the Southeastern United States:
A broad area of low pressure is forecast to form in a couple of 
days a few hundred miles off the coast of the southeastern United 
States. Some gradual development of this system is possible during 
the middle or latter part of the week as the system drifts to the 
west or northwest. 
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...30 percent.

[WxWatcher007]

8 hours ago, GaWx said:

Upped from 20% to 30%:

2. Off the Southeastern United States:
A broad area of low pressure is forecast to form in a couple of 
days a few hundred miles off the coast of the southeastern United 
States. Some gradual development of this system is possible during 
the middle or latter part of the week as the system drifts to the 
west or northwest. 
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...30 percent.

Interesting that the model signal is still there but backed off some after being more aggressive yesterday. 

[WxWatcher007]

12z Euro was a bit more robust at 850mb. Gets a good bit of rain into NC and points north. 

I think that much like Dexter, models could be playing catch up with this if there is a pocket of lighter shear available to the eventual low.

[WxWatcher007]

A little surprised that the EPS was so bullish on the disturbance at 12z. Very high odds of a TD with modest odds of a TS. Note where the highest probabilities are.

[BarryStantonGBP]

1. Off the Southeastern United States:
A weak surface trough currently located several hundred miles off 
the coast of the southeastern United States is expected to form an 
area of low pressure in a day or so. Thereafter, environmental 
conditions appear favorable for gradual development of this system, 
and a tropical depression could form by the latter portion of this 
week or weekend as as the low initially moves slowly westward, but 
turns more northward by this weekend.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...medium...40 percent.

[Kevin Reilly]

On 8/3/2025 at 1:47 PM, WxWatcher007 said:

Ok, so normally we wouldn't have threads for current low probability systems, but I guess we're changing that this year. This comes from my bigger overview, which highlights this area of interest. I've been quietly watching for days, and now it's worth discussion. 

This area of potential has been much more interesting than 95L, and has been for a while now for the reasons below. Yesterday most probably sat up as the happy hour GFS showed a strong system attempt to develop in the wake of 95L off the same frontal boundary, this time getting shunted back into the US. Well, although that run of the GFS was way too aggressive, the signal for some sort of follow up development has been on the guidance for a few days now. It's not terribly hard to see why, as the environment looks at least marginally favorable for some development. 

Vorticity

First--the frontal boundary is usually good for getting some vorticity spin up. This fits with climatology. So if something is far enough off the coast there should be some sort of spin that develops in the coming days. Both models pick up on this in the medium range. 

This is not enough for TC genesis. Which leads to the second favorable factor.

Instability

While the tropical Atlantic has been incredibly stable so far this season...

There has been no such issue off the East Coast...in fact, instability has been extremely high. 

What that tells me is that anything that does have spin and can develop an area of low pressure will have a chance to generate convection, which will only help with TC genesis odds as long as the system isn't hugging land the entire time. 

SSTa

Not much analysis needed here. I expect the the southwest Atlantic to be a hotbed of activity this season because that's where the heat is. Any low is going to have a shot with enough time and space to become tropical in this SSTa regime. 

Shear

The key inhibitor here is shear. Often times with these frontal boundary systems near the coast you have shear and drier air that is lurking. That comes with the territory with the frontal boundary. Here it is unclear how favorable a shear environment this potential system will find, but guidance is hinting at a window of lower shear later this week taking hold. 

What makes this particularly interesting is the steering pattern. While the outcome is different in terms of where the area of vorticity goes, the pattern evolution is the same. In the wake of 95L a ridge builds in and traps whatever could develop along the coast. That's something to legitimately watch. Maybe not closely, yet, but at least with a casual eye.  

Sea Surface temps up the east coast are a bit concerning for a tropical system IF atmospheric conditions are right to maintain its energy well northward up the coast.   Now with how wet it has been minus the last week in the Mid Atlantic up to NYC and northern New Jersey could be setting up for a few rough weeks from now until say August 25th depending on what both systems do up the East Coast.

 

System #1 Late week into the weekend and early next week

System #2 August 15th to 20th sitting out in the western MDR right now.

 

Case in point I am in Kitty Hawk NC right now and ocean water temps have been running 82-85 on the regular since I have been here Saturday.

[BarryStantonGBP]

1 hour ago, Kevin Reilly said:

Sea Surface temps up the east coast are a bit concerning for a tropical system IF atmospheric conditions are right to maintain its energy well northward up the coast.   Now with how wet it has been minus the last week in the Mid Atlantic up to NYC and northern New Jersey could be setting up for a few rough weeks from now until say August 25th depending on what both systems due up the East Coast.

 

System #1 Late week into the weekend and early next week

System #2 August 15th to 20th sitting out in the western MDR right now.

 

Case in point I am in Kitty Hawk NC right now and ocean water temps have been running 82-85 on the regular since I have been here Saturday.

Google DeepMinds has systems all the way from Erin to fucking Humberto